Fuse mechanism



March 19, 1929. $AND|N v 1,705,685

FUSE MECHANISM Filed July 11. 1922 I l I? 6. --J y i 26V 29 1 "1 v W n; 2a WITNESSES: v INVVIENTOR. M. Maur'ns J bar/din.

ATTORNEY Patented Mar. '19, 1929.

UNITED STATES PATEN T OFFICE.

MAURI'I'S J'. SANDIN, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR T0 WESTING- & MANUFACTURING HOUSE ELECTRIC VANLA.

Application filed July 11,

from the casing. This invention relates particularly to'an improved form of fuse strip that is adapted for incorporation in an expulsion fuse of the type disclosed in the above application, but which may be incorporated in expulsion fuses of any preferred type, with or without an inner insulating tube.

One object of my invention is to provide an expulsion fuse that is quickly effective in interrupting a circuit carrying an abnormal current, caused by overload or short-circuit conditions.

Another object of my invention is to provide an expulsion-fuse mechanism wherein the fuse strip is divided into a plurality of flexible strands which may readily be dis- ,placed and discharged from the fuse casing by the arc gases produced by the interruption of a high-potential circuit.

Another object of my invention is to provide an expulsion fuse wherein the strips may be accurately made of uniform capacity and which will be fused under similar predetermined current conditions.

Another object of my invention isto provide an expulsion fuse wherein a fuse strip may readily be replaced with a minimum expenditure of effort.

Another object of my invention is to provide an expulsion fuse wherein the fuse is encased in a tubular member that is adapted to be expelled by the arc gases for the purpose of elongating the are under overload conditionsin the circuit and Wherein'the fusible strip is provided with an unusually large current-carrying portion that ordinarily is of greater width than the internal diameter of the tube but which is folded or curved in order that it may be inserted within the tube: By reason of the large current-carrying capacity of the fuse strip and the large radiating surface thereof, rupture of the fuse is insured at a point adjacent the closed end COMPANY, A CORPORATION OF PENNSYL- FUSE MECHANISM.

192a. Serial No. 574,199.

of the casing where the current-carrying capacity of the fuse strip is relatively small and charrmg of the insulating tube is prevented under normal service conditions because the fuse is maintained at a relatively low temperature.

These and other objects, that will be made apparent throughout the further description of my lnvention, are attained by means of the fuse mechanism hereinafter described, and

illustrated in the accompanying drawings,

wherein:

Figure 1 is a longitudinal section through the expulsion-fuse mechanism Fig. 2 is an elevational view of an improved form of fuse strip, showing its relation to a tubular member;

Fig. 3 is a transverse section through the iuse strip, taken on the line III-*III of ig. 4 is a transverse section through the fuse strip, taken on the line IVIV of Fig. 2;

Fig. 5 is a transverse section through the fuse strip, taken on the line VV of Fig. 2; Fig. 6 is anielevational view of a fragment of the blank from which the fuse illustrated in Figs. 1 and 2 is formed;

ig. 7 is a transverse section through the fuse mechanism, taken on the line VII-VII of Fig. 1, and

Fig. 8 is a perspective view of a modified form of fuse strip.

Referring to the drawings, the fuse mechanism includes a casing 9 made of insulating material, such, for instance, as micarta. One end of the tube 9 is threaded to receive a threaded metallic sleeve 11, which constitutes a terminal member adapted to be inserted in a fuse clip which may be of any preferred construction.

The lower end of the casing 9 is provided with a terminal sleeve 12 having a lock 13 for engaging a terminal clip, such as is illustrated in the above-mentioned co-pending application. The upper end of the casing is closed by means of a cap 14 which is threaded upon the sleeve 11. A fuse terminal 15 is secured to the sleeve 11 and is provided with a pair of threadel holes 16, which receive clamping screws 17 of the fuse-clamping device. The upper end of .a fuse strip '18, which will be hereinafter more fully described, is clamped between the terminal 15 and a plate 19, by means of the screws 17 disposed at opposite edges of the fuse strip.

The fuse strip comprises a flat strip that may be stamped from sheet metal of any predetermined thickness, depending upon the desired capacity.

Fig. 6 illustrates a blank from which a strip is formed. It will be seen that the strip comprises a relatively narrow portion 21 and a relatively wide portion 22. The one end of the wide portion is split at 23 along the length thereof, as indicated in Fig. 6. The strip is then so folded on the line 24 that the split pprtions; lie side by side and engage one another.

This construction provides a relatively flexible portion of the fuse strip having a relatively large current-carrying capacity compared with the reduced section 21. The increased flexibilityis of considerable importance in an expulsion fuse where the arc gases are utilized to expel the unfused portions of the fuse strip from the open end of the casing.

It has been found that, where single-strand fuse strips are employed, having sufficient capacity to prevent rupture of the fuse except at the narrow portion, the gases are unable to properly crumple or bend the fuse strip, with the result that it is not discharged from the casing and sustains the arc until it is entirely consumed. i 3

By increasing the flexibility of the fuse and, at the same time, increasing its capacity at the flexible portion, proper operation of the fuse is insured, that is, the fuse is caused to rupture at the portion of reduced cross section and the remainder of the fuse is expelled instantly from the casing.

This form of fuse strlp is particularly well adapted for use in an expulsion fuse of the type illustrated in the above-mentioned co-' pending application, wherein an insulating tubular member 25 surrounds the fuse strip and is adapted to be expelled by the arc gases. Where such a tube is used, the lower end of the fuse strip is bent upwardly in such manner that it retains the tube within the casing.

The lower end of the fuse is secured to the sleeve 12 by means of a clamping plate 26 that is attached to the sleeve by means of screws 27.

Under certain overload and short-circuit conditions, the strip first fuses at the reduced portion 21 and theheated gases blowing past the bent portion of the fuse adjacent the mouth of the tube melt it and release the tube 25, which is then instantly expelled. However, under certain current conditions, the outer end of the fuse may not be melted instantly and, in this event, the flexibility of the fuse strippermits the tube 25 to displace the fuse strip and drive it out of the tube 9, thus I elongating and extinguishing the arc. It has been found that this construction is particularly well adapted for overload protection in high-potential circuits and that it successfully operates on relatively small overloads as well as severe short circuits.

In the device shown in the co-pending application above referred to, a wing 28 is attached to the lower ,end of the tube 25 which is engaged by the expelled gases and serves to assist in forcing the tube from the casing. The wing 28 consists of a metal stamping, such. as is shown in Figs. 1 and 7, having side portions 29 that are adapted to be bent into notches 31 on opposite sides of the tube 25. This construction provides a simple and effective means for attaching the wing 28 to the tube.

. The reduced end 21 of the fuse strip 18 is provided with an enlarged portion 32 of greater width than the internal diameter of thetube 25. By reason of this enlarged portion, greater contact surface is provided and the fuse strip is prevented from passing through the tube. This construction is of assistance while attaching a-fuse within the' The cap 14 isremoved from the sleeve 11 to expose the terminal 15. The tube 25 is then inserted in the lower end of the casing 9 and the enlarged portion 32 of the fuse is then clamped to the terminal 15. The free end of .the fuse is then bent into engagement with the terminal 12 and secured thereto.

In Fig. 8, I have illustrated a modified form of fuse strip which is made from a flat sheet of metal and which comprises a relatively wide portion 33 and narrow terminal portions 34 and 35, the'former being of greater capacity than the latter to insure rupture first at theinner end of the fuse. The wide portion is bent into the" form of a cylinder to reduce its tranverse dimension so that it may be inserted into the tube 25. The wide portion of the strip, before it is bent, is indicated in dotted lines in Fig. 8.

When certain overload conditions occur,

the strip 33 fuses at the reduced portion 35 and burns away sufficient metal to open the circuit. Under more severe conditions, the

are first starts at the reduced portion 35 and i the gases melt the portion 34, thus releasing the body of the fuse which is blown violently from the cartridge.

While I have described and illustrated but two embodiments of my invention, it will be apparent to those skilled in the art that various changes, modifications, substitutions,

' additions and omissions maybe made therein without departing from the spirit and scope of my invention, as set forth in the appended claims.

I claim as my invention: 1. A fuse member comprising a flat fusible metallic strip having a relatively narrow integral terminal portion and a relatively \vide body portion folded throughout its entire length to reduce its width.

2. A fuse member comprising a flat fusible metallic strip having a portion folded longitudinally to reduce its width, the said strip being split to separate a greater portion of the folded portions.

3. A fuse member comprising a fusible fiat metallic strip having a portion split throughout a greater portion of its length into relatively movable portions one of which has a reduced portion.

. 4. A fuse member comprising a flat, relatively long fusible strip slotted longitudinally throughouta greater portion of its length to increase its flexibility.

5. A fuse structure comprising a tubular member and a fusible strip of greater width than the internal diameter of the tubular member and folded along its length to so reduce its width that it can be inserted lengthwise in the tube, and provided with a portion of greater Width than the said folded portion to prevent its passage through the tube.

6. A fuse member comprising a flat fusible member split longitudinally for a portion of its length and folded along a portion of the unsplit portion to bring the folded portions in face-to-face relation.

7. A fuse structure comprising a tubular member and a fusible strip of greater width than the internal diameter of the tubular member and warped to so reduce its Width that it can be inserted lengthwise in the tube and provided with a portion of greater diameter than the said width to prevent its passage through the tube.

In testimony whereof I have hereunto subscribed my name this 3 day of July, 1922.

MAURITS J. SANDIN. 

